1. Field of Invention
The present invention relates to a power regulator circuit, and more particular to a power regulator with a constant-voltage output.
2. Related Art
As the rapid development of the electronic technology, one electronic system includes various functional circuits with different sizes (e.g., rectifier, filter, transformer, regulator, signal converter, or signal amplifier). In order to enable the electronic system to work normally, power management must be utilized, so as to control and maintain the normal supply of an appropriate current and voltage within the electronic system at any time under different operation states of the electronic system.
The power management circuit is divided into various types, including power regulator, cell charging/measurement, hot plug, and voltage monitor. The power regulator is mainly used for supplying a stable output voltage to the electronic system when the voltage and current of the load of the power supply are changed. However, when being applied in a high precise reference voltage output with a small current, the power regulator is easily affected by a loading effect, so that the output precision is reduced, which has been a problem to be solved as for the high quality design trend.
With reference to Taiwan Patent Publication No. 200419319, a pulse width modulation (PWM) voltage regulator is disclosed, which includes a PWM circuit and a control circuit. The control circuit is operated for reducing the pulse modulation frequency of the PWM circuit, when the current of the load increases, and operated for increasing the pulse modulation frequency of the PWM circuit, when the current of the load decreases.
Although the above patent application can adjust the pulse modulation frequency of the PWM circuit correspondingly according to the change of the current of the load, so as to reduce the power consumption and improve the voltage regulating efficiency, the above control circuit is only applicable for a regulator with a PWM circuit, and thus, it is quite limited in the circuit application scope.
Therefore, when the current of the load changes, the current of the power regulator of the previous stage circuit is affected, so that the problem that the output voltage of the power regulator is affected by the loading effect and thereby being imprecise occurs.